Mal formed XML Response when inserting Accounts with option &duplicateCheck=(1)&version=4

Mal formed XML Response when inserting Accounts with option &duplicateCheck=(1)&version=4

Hi,
when I'm inserting multiple records in accounts with the option "&duplicateCheck=(1)&version=4" sometimes I receive a wrongly formed xml which is missing a starting tag , the example where the starting <row no="97">  is missing.

I'm using the duplicate option because the multiple insert is not returning the response which will provide enough information to map the request and response which is crucial in my case.

With Mal formed response i have even more problems... any advice ?

regards
Tomaz